// Google Authenticator
// 只从google出了双重身份验证后，就方便了大家，等同于有了google一个级别的安全，但是我们该怎么使用google authenticator (双重身份验证)，
// 下面是java的算法，这样大家都可以得到根据key得到公共的秘钥了,直接复制，记得导入JAR包：
// commons-codec-1.xx.jar

// 使用方法：
// 1、main生成一个KEY（用户为testuser），URL打开是一张二维码图片。
// 2、在手机中下载“GOOGLE身份验证器”。
// 3、在身份验证器中配置账户，输入账户名（第一步中的用户testuser）、密钥（第一步生成的KEY），选择基于时间。
// 4、运行authcode方法将key和要测试的验证码带进去（codes，key），就可以知道是不是正确的秘钥了！返回值布尔

package me.exchange.com.utils;

import cn.hutool.extra.qrcode.QrCodeUtil;
import cn.hutool.extra.qrcode.QrConfig;
import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 *
 *
 * google身份验证器，java服务端实现
 *
 * @author yangbo
 *
 * @version 创建时间：2017年8月14日 上午10:10:02
 *
 *
 */
public class GoogleAuthenticator {

    // 生成的key长度( Generate secret key length)
    public static final int SECRET_SIZE = 10;

    public static final String SEED = "g8GjEvTbW5oVSV7avL47357438reyhreyuryetredLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
    // Java实现随机数算法
    public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";
    // 最多可偏移的时间
    int window_size = 3; // default 3 - max 17

    /**
     * set the windows size. This is an integer value representing the number of
     * 30 second windows we allow The bigger the window, the more tolerant of
     * clock skew we are.
     *
     * @param s
     *            window size - must be >=1 and <=17. Other values are ignored
     */
    public void setWindowSize(int s) {
        if (s >= 1 && s <= 17)
            window_size = s;
    }

    /**
     * Generate a random secret key. This must be saved by the server and
     * associated with the users account to verify the code displayed by Google
     * Authenticator. The user must register this secret on their device.
     * 生成一个随机秘钥
     *
     * @return secret key
     */
    public static String generateSecretKey() {
        SecureRandom sr = null;
        try {
            sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
            sr.setSeed(Base64.decodeBase64(SEED));
            byte[] buffer = sr.generateSeed(SECRET_SIZE);
            Base32 codec = new Base32();
            byte[] bEncodedKey = codec.encode(buffer);
            String encodedKey = new String(bEncodedKey);
            return encodedKey;
        } catch (NoSuchAlgorithmException e) {
            // should never occur... configuration error
        }
        return null;
    }

    /**
     * Return a URL that generates and displays a QR barcode. The user scans
     * this bar code with the Google Authenticator application on their
     * smartphone to register the auth code. They can also manually enter the
     * secret if desired
     *
     * @param user
     *            user id (e.g. fflinstone)
     * @param host
     *            host or system that the code is for (e.g. myapp.com)
     * @param secret
     *            the secret that was previously generated for this user
     * @return the URL for the QR code to scan
     */
    public static String getQRBarcodeURL(String user, String host, String secret) {
        String format = "http://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s?secret=%s";
        return String.format(format, user, host, secret);
    }

    /**
     * 生成一个google身份验证器，识别的字符串，只需要把该方法返回值生成二维码扫描就可以了。
     *
     * @param user
     *            账号
     * @param secret
     *            密钥
     * @return
     */
    public static String getQRBarcode(String user, String secret) {
        String format = "otpauth://totp/%s?secret=%s";
        return String.format(format, user, secret);
    }

    /**
     * Check the code entered by the user to see if it is valid 验证code是否合法
     *
     * @param secret
     *            The users secret.
     * @param code
     *            The code displayed on the users device
     * @param timeMsec
     *            The time in msec (System.currentTimeMillis() for example)
     * @return
     */
    public boolean check_code(String secret, long code, long timeMsec) {
        Base32 codec = new Base32();
        byte[] decodedKey = codec.decode(secret);
        // convert unix msec time into a 30 second "window"
        // this is per the TOTP spec (see the RFC for details)
        long t = (timeMsec / 1000L) / 30L;
        // Window is used to check codes generated in the near past.
        // You can use this value to tune how far you're willing to go.
        for (int i = -window_size; i <= window_size; ++i) {
            long hash;
            try {
                hash = verify_code(decodedKey, t + i);
            } catch (Exception e) {
                // Yes, this is bad form - but
                // the exceptions thrown would be rare and a static
                // configuration problem
                e.printStackTrace();
                throw new RuntimeException(e.getMessage());
                // return false;
            }
            if (hash == code) {
                return true;
            }
        }
        // The validation code is invalid.
        return false;
    }

    private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
        byte[] data = new byte[8];
        long value = t;
        for (int i = 8; i-- > 0; value >>>= 8) {
            data[i] = (byte) value;
        }
        SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(signKey);
        byte[] hash = mac.doFinal(data);
        int offset = hash[20 - 1] & 0xF;
        // We're using a long because Java hasn't got unsigned int.
        long truncatedHash = 0;
        for (int i = 0; i < 4; ++i) {
            truncatedHash <<= 8;
            // We are dealing with signed bytes:
            // we just keep the first byte.
            truncatedHash |= (hash[offset + i] & 0xFF);
        }
        truncatedHash &= 0x7FFFFFFF;
        truncatedHash %= 1000000;
        return (int) truncatedHash;
    }

    /**
     *
     *
     * 身份认证测试
     *
     * @author yangbo
     *
     * @version 创建时间：2017年8月14日 上午11:09:23
     *
     *
     */
    public static void main(String[] args) {

        //当测试authTest时候，把genSecretTest生成的secret值赋值给它
        String secret="SWCDDQXDGIQPHOSA";
        secret = GoogleAuthenticator.generateSecretKey();
        // 把这个qrcode生成二维码，用google身份验证器扫描二维码就能添加成功
        String qrcode = GoogleAuthenticator.getQRBarcode("admin", secret);

        // String qrcode = GoogleAuthenticator.getQRBarcodeURL("admin","交易所后台管理",secret);
        BufferedImage image = QrCodeUtil.generate(qrcode,new QrConfig());
        //转换成png格式的IO流
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
       try {
           ImageIO.write(image, "jpg", out);
       }catch (Exception e) {
           e.printStackTrace();
       }
        byte[] bytes = out.toByteArray();
        // 2、将字节数组转为二进制
        /**
         *  /lib/tool.jar和/lib/rt.jar已经从Java SE 9中删除
         *  import java.util.Base64.Encoder;
         *  Encoder encoder = Base64.getEncoder();
         *  String result = encoder.encodeToString(bytes);
         */
        String binary = Base64.encodeBase64String(bytes).trim();

        System.out.println("qrcode:" + qrcode + ",key:" + secret);
        System.out.println("qrcode_img:data:image/jpg;base64," + binary);
        /**
         * 对app的随机生成的code,输入并验证
         */

        secret = "P5G3ONW765CQHLAV";
           long code = 479722;
            long t = System.currentTimeMillis();
            GoogleAuthenticator ga = new GoogleAuthenticator();
            ga.setWindowSize(5);
            boolean r = ga.check_code(secret, code, t);
            System.out.println("检查code是否正确？" + r);
    }
}